Cement Grouting in cracks in concrete and masonry:

Wide  cracks,  particularly  in  mass  concrete  abutments / piers  and  masonry substructures  can be  repaired  by  filling  with  portland  cement  grout.  This method  is  effective  in  sealing  the  crack  in  concrete,  but  it  will  not structurally  bond  cracked  sections.

 Applications of cement grouting:

i)  When cracks are dormant

ii)  Cracks  are  active  but  cause  of  cracking  has  been  determined  and remedial action has been taken.

iii)  When honeycombing is present in concrete structures.

iv)  When masonry is hollow.

v)  When deep leached mortar joints are present.

Materials proportion and pressure of grouting in cracks:

Ordinary  Portland  cement  to  IS:269,  sand  and  water  are  required.    Admixtures  to  impart  non-shrinkable  properties  and  to  improve flowability of grout may be added.  The method of using admixture may be as  per  the  manufacturer’s  recommendations.  The  water-cement  ratio  (by weight) for the grout should be 0.4 to 0.5, the lower ratio being used when crack  width exceeds 0.5mm.  In atypical  mix proportion for grout, 20 litres of  water  to  be  mixed  with  50  kg  of  cement  along  with  225  gms  of  non shrink  admixture,  such  as  conbex  100  (of  M/s  Fosroc),  should  be  used.

The grouting pressure should be 2 to 4 kg/cm2.

Fig: Procedure for pressure grouting of concrete

Equipment for cement grouting in cracks:

The equipment required for cement pressure grouting are:

i)  Air compressor with a capacity of 3 to 4 cum/ per minute and with a pressure of 2 to 4 kg per sq.cm.

ii)  Grout  injecting  machine  or  grouting  pump  with  inlet  and  outlet valves  and  pressure  gauges.  It  should  be  capable  of  injecting cement  grout  up  to  4  kg/cm2(Now  up  to  20  kg/cm2 pumps  are available).

iii)  An  air  tight,  pressure  mixer  chamber,  with  stirrer  for  proper  mixing of  the  grout  and  keeping  it  in  proper  colloidal  suspension  during grouting.

iv)  Flexible  pressure  hose  pipes  for  transmitting  grout  from  pressure chamber to ports embedded in the masonry.

v)  Drilling  equipment,  pneumatic  or  electric,  for  drilling  of  holes  upto 25mmdia.

vi)  12-20mm  dia  G.I.  pipes  with  couplers,  or  lockable  type  PVC nozzles.

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